public class EncryptAndDecrypt {   

   String encrypt(String sourceString,String password) { //加密算法

       char [] p= password.toCharArray();

       int n = p.length;

       char [] c = sourceString.toCharArray();

       int m = c.length; 

       for(int k=0;k<m;k++){

            int mima=c[k]+p[k%n];       //加密

            c[k]=(char)mima; 

       }

       return new String(c);    //返回密文

    }

    String decrypt(String sourceString,String password) { //解密算法

       char [] p= password.toCharArray();

       int n = p.length;

       char [] c = sourceString.toCharArray();

       int m = c.length; 

       for(int k=0;k<m;k++){

           int mima=c[k]-p[k%n];       //解密

           c[k]=(char)mima; 

       }

       return new String(c);    //返回明文

   }

}
